Initial increase in blood CD4+ lymphocytes after HIV antiretroviral therapy reflects redistribution from lymphoid tissues

Abstract

Previous studies proposed a dynamic, steady-state relationship between HIV-mediated cell killing and T-cell proliferation, whereby highly active antiretroviral therapy (HAART) blocks viral replication and tips the balance toward CD4⁺ cell repopulation. In this report, we have analyzed blood and lymph node tissues obtained concurrently from HIV-infected patients before and after initiation of HAART. Activated T cells were significantly more frequent in lymph node tissue compared with blood at both time points. Ten weeks after HAART, the absolute number of lymphocytes per excised lymph node decreased, whereas the number of lymphocytes in the blood tended to increase. The relative proportions of lymphoid subsets were not significantly changed in tissue or blood by HAART. The expression levels of mRNA for several proinflammatory cytokines (IFN-γ, IL-1β, IL-6, and macrophage inflammatory protein-1α) were lower after HAART. After therapy, the expression of VCAM-1 and ICAM-1 — adhesion molecules known to mediate lymphocyte sequestration in lymphoid tissue — was also dramatically reduced. These data provide evidence suggesting that initial increases in blood CD4⁺ cell counts on HAART are due to redistribution and that this redistribution is mediated by resolution of the immune activation that had sequestered T cells within lymphoid tissues.